Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : March 10, 2021 - March 11, 2021
Mod.9Cr-1Mo steels are widely being used for steam pipes in ultra-super critical power plants. Creep damages, such as void initiation and growth, were detected at heat affected zone (HAZ) in welding portions. It is necessary to clarify creep damage extension mechanism and life prediction method in the welded portions. In this study, round bar tensile type miniature specimens with 1mm diameter were machined from a base metal, a weld metal and a HAZ in a shieled metal arc welding pipe. Material constants of Norton’s law were determined from creep tests using the miniature specimens. Creep tests were also conducted using standard size welded joint creep specimens taken from the pipe. The welded joint specimens were failed at the HAZ and rupture times of the weld joints were shorter than those of the base metals. Void initiation and growth were observed at the HAZ. A finite element creep analysis for the welded joint specimen was performed using material constants obtained by the miniature specimens. It indicated that higher stress and creep strain concentrate at the HAZ causing void initiation and shorter rupture time than the base metal.
